The invention is directed to an apparatus for the production of particular concentrations of gaseous materials as well as for mixing various gaseous materials in a specified ratio.
In many cases it is necessary to produce gaseous mixtures of arbitrary composition and concentration. For example, the equipment used to measure air contamination must be calibrated. This requires special care. Since very small measurement ranges must be calibrated in the case of automatically operating emission stations, for which in most cases cylinders of compressed test gas cannot be produced, dynamic methods of producing test gases are almost always used. To ensure a supply of accurate and reliable test gas mixtures also in these cases, gas mixing equipment is required, with which even calibrations below 1 ppm are possible with great precision.
To control the temperature of water in engine cooling system heat exchangers, it is known to use a magnetic valve controllable by means of a relay (German Patent Publication (DAS) No. 2,840,431). This magnetic valve controls an actuator, which in turn controls a closing member. In this case, the closing member is a cam disk valve, which is movable diagonally between two adjacent arms of a cross-shaped part and opens or closes off several paths.
A similar valve which has two outlets and one inlet is disclosed in the German Patent Publication (DOS) No. 2,126,485. Here also, the valve serves to control the temperature of a liquid.
In a known arrangement for the controlled metering of two or more gases, which are connected over two separate lines with sources for the gases that are to be mixed in a specified ratio, fast acting and electrically controlled on-off valves are clocked in a set time-slot pattern in the separate lines (German Patent Publication (DAS) No. 2,831,856), to which U.S. Pat. No. 4,262,686 corresponds).
In this case, the gases are supplied in pulsed fashion and either the width of the individual gas pulses or the number of pulses per unit time is varied. Nothing is mentioned concerning the generation of pressure, which is necessary for the flow of the gases.
In a different previously known method for mixing gases in a specified ratio, the gases are supplied in pulsed fashion to the mixing space (European Patent No. A1 0 065 271, to which U.S. Pat. No. 4,526,188 corresponds). The ratio of the pulse volumes of the different gases is the same as the desired ratio of the gases in the mixture. Special compressed gas sources provide for the flow of the gas.
Finally, a gas mixing apparatus is also known, in which the proportions of gases supplied over component feeding pipes is adjustable. In this apparatus, the proportion of a gas component is determined by the duration of the gas flow through a throttle valve before and after which the pressure is constant (German Patent Publication (DAS) No. 3,135,455). To improve the accuracy of the measurement, a common throttle valve for the components is disposed in the feeding pipe to a buffer vessel. The throttle valve site can be connected over a controllable multi-way valve with the individual feeding pipes for the components. A pressure regulating valve, which is connected with an receiver line for the gas mixture, is disposed downstream from the buffer vessel. The pressure, necessary for the flow of the gas, is produced by pressure pumps disposed upstream. This is disadvantageous, because the output of a pump depends on the type of gas.